This is a competitive renewal of the New York Obesity Research Center (ORC). The ORC integrates the obesity research programs situated at the Rockefeller University and the St.Luke's-Roosevelt Hospital Center. The ORC is adding to the program two new Core Laboratories from Cornell Medical College, one a mass spectrometry facility and the other a leading laboratory of ingestive behavior. Objectives of the combined center include the following: (i) to bring together under the Center's aegis, a critical mass of independent investigators of separately funded research projects who share a strong interest in the study of obesity-related problems; (ii) to use funds available for support of pilot and feasibility (P/F) projects and program enrichment activities to promote and test new research ideas, stimulate productivity, foster the development of talented new investigators in the field, and persuade creative scientists working in areas or disciplines not ordinarily concerned with obesity to become involved in obesity-related research; (iii) to provide participating investigators of funded projects relevant to obesity research with valuable laboratory, technical and educational services that otherwise would not be available, thereby improving productivity and efficiency of their operations, and (iv) by maintaining a dynamic focus for obesity-related investigation, to move the field more effectively into basic and applied research critical to the solution of key problems. The administrative core will provide a structure for peer evaluation of P/F protocols, training initiatives, biostatistical/computational services and an enrichment program. Eight research cores offer a comprehensive spectrum of services; funding is requested for 5 of them: (i) a body composition and energy expenditure core; (ii) a core for measurement of hormones and metabolites; (3) an adipose tissue and molecular biology core; (4) an ingestive behavior core; and (5) a mass spectrometry core. No funding is requested for the other three cores: (6) an inpatient core for conduct of rigorously controlled metabolic studies; (7) a core for clinical investigation on obese outpatients; (8) and a respiratory chamber-indirect calorimeter.